High Quality Stepped-Impedance Resonators Suitable for Circuit-QED Measurement of Superconducting Artificial Atoms

TL;DR

This paper presents the design, fabrication, and measurement of stepped impedance resonators (SIRs) that are more compact than traditional uniform impedance resonators (UIRs), maintaining high quality factors suitable for superconducting quantum circuits.

Contribution

The paper introduces a novel SIR design that reduces resonator size by 27% while preserving high quality factors, enhancing circuit integration in quantum computing.

Findings

SIRs are 27% shorter than UIRs with comparable quality factors.

SIRs maintain Qi around half-million at single-photon levels.

Reduced size of SIRs enables more compact quantum circuit designs.

Abstract

High quality factor coplanar resonators are critical elements in superconducting quantum circuits. We describe the design, fabrication and measurement of stepped impedance resonators (SIRs), which are more compact in size than commonly used uniform impedance resonators (UIRs). With properly chosen impedance ratio, SIRs can be 27% shorter than UIRs. As a result, the area occupied by SIRs can be reduced. Two kinds of designs containing both SIRs and UIRs are fabricated and measured. The power dependence of the extracted internal quality factors (Qi) for all the resonators showed that SIRs and UIRs have comparable performance with Qi around half-million under single-photon level excitation. These results indicate that SIRs could be used in superconducting quantum circuits. The reduced size of SIRs may also lead to reduced overall circuit area and increased integration level.